This paper focuses on reservoir’s constructive systems for municipal water supplies in Portugal and Europe between 1820 and 1880. It particularly examines the use of “betón”, an unreinforced concrete, which was developed in the 19th century. The increase in the number of people living in cities at the time led to the construction, as well as the modernisation of drinking water supplies systems, including the construction of new reservoirs to store drinking water prior to its distribution. Reservoirs are an essential component of water supply systems, and their design remained unchanged until the 19th century. The main changes occurred when new types of cement, such as natural cement or agglomerated concrete, were developed and applied in mortars and concrete, as well as new waterproofing materials. Nowadays, not only is it unknown how many reservoirs were built with this type of cement, but also where it came from. This lack of knowledge jeopardises the correct rehabilitation of buildings from that era. The aim of this study is to address this issue by providing a systematic overview of the constructive systems and innovative materials implemented in the second and third quarters of the 19th century, with the goal of facilitating their proper restoration or reconstruction.